Molding material and molded article for laser fusion

ABSTRACT

A molding material and a molded article for laser welding are provided, which comprise a thermoplastic resin (A) comprising a rubber-reinforced resin (A1) obtained by polymerizing a vinyl monomer in a presence of a rubber-like polymer (a), or a composition (A2) of the rubber-reinforced resin (A1) and a (co)polymer (b) of a vinyl monomer, and which have a light transmittance at a wavelength of 808 nm in a range of 5% or higher when molded into a 4 mm-thick sample piece. The rubber-like polymer (a) dispersed in the thermoplastic resin (A) preferably has a weight average particle size of 50 to 220 nm, and preferably comprises particles of 300 nm or larger in diameter in an amount of 0 to 20 wt % relative to 100 wt % of the component (a). A laser light can transmit the molding material and the molded article, and allow the molding material and the molded article to be laser-welded with various resin moldings.

This Application is the National Phase of International Application No.PCT/JP2004/000791 filed Jan. 29, 2004, which designated the U.S. and wasnot published under PCT Article 21(2) in English, and this applicationclaims, via the aforesaid International Application, the foreignpriority benefit of and claims the priority from Japanese ApplicationNo. 2003-026659, filed Feb. 4, 2003, the complete disclosures of whichare incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to molding materials and molded articlessuitable to be joined by laser welding, and particularly to moldingmaterials and molded articles containing rubber-reinforced resins.

BACKGROUND ART

As methods for joining molded articles made of thermoplastic resinstogether, welding techniques have conventionally been known includinghot plate welding, vibration welding, ultrasonic welding and laserwelding, aside from methods that employ fastening parts (bolts, screws,clips and the like) or adhesives. The hot plate welding is a techniquein which areas to be welded of molded articles are brought into contactwith heated plates so as to be molten, and the molten areas are pressedagainst each other before cooling and solidifying. However, thistechnique often forms threads when the areas to be welded are separatedfrom the heated plates, affecting appearance of molded articles. Thevibration welding and ultrasonic welding are techniques in which onearticle is fixed, and the other article is pressed thereon whilevibration or ultrasonic wave is applied, so that the areas to be weldedare molten and welded by friction energy. However, these techniquesoften cause dust and thread-like flashes in the welded areas or causebent flashes or other problems. As a result, molded articles are oftendegraded in appearance and become unusable depending on shape of thearticles.

The laser welding is a method in which one of the articles to be weldedis formed of a laser-absorbing material whilst the other is formed of alaser-transmitting material, and they are stacked together and thensubjected to irradiation with laser light on the side of thelaser-transmitting material. Thus, the laser light which has passedthrough the transmitting material heats up and melts the surface of thelaser-absorbing material, and also melts the laser transmitting materialby heat transfer, so that the two resins are welded together (See,Japanese Patent Laid-Open Publication No. 2001-71384). This technique isadvantageous in that no threads, dust or flashes are formed, theresulting welded areas have good appearance, and it can be used to weldmolded articles of various shapes. Nonetheless, the technique has alimitation in that one of the articles to be welded must be formed of alaser-transmitting molding material

Rubber-reinforced styrenic resins represented byacrylonitrile-butadiene-styrene (ABS) resins, high impact polystyrenes(HIPS) and the like are excellent in mechanical properties, physicalproperties, electrical properties and the like, and are therefore usedin a wide range of fields such as of electrics or electronics, officeautomation or household electrical appliances, automobiles, and sanitaryfittings. However, these resins are low in transmittance of laser lightand therefore cannot be used in laser welding unless they are weldedwith an article made of a laser-transmitting material.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide moldingmaterials and molded articles which comprise a thermoplastic resincontaining a rubber-reinforced resin and which can transmit laser lightand thus can be laser-welded to various resinous molded articles.

The present inventors have intensively studied rubber-reinforced resinsin terms of particle size and its distribution of rubber-like polymersdispersed in the resins and, as a result, have found that when theparticle size and distribution thereof fall in particular ranges, therubber-reinforced resins transmit laser light sufficiently to belaser-welded. Thus, the present invention has been completed.

Specifically, in accordance with one aspect of the present invention,there is provided a molding material for laser welding, comprising athermoplastic resin (A) which comprises:

a rubber-reinforced resin (A1) obtained by polymerizing a vinyl monomerin a presence of a rubber-like polymer (a),

or a composition (A2) comprising said rubber-reinforced resin (A1) and a(co)polymer (b) of a vinyl monomer,

wherein said molding material has a light transmittance at a wavelengthof 808 nm in a range of 5% or higher when the material is molded into a4 mm-thick sample piece. From the viewpoint of laser-weldability, theabove light transmittance is preferably 7% or higher, more preferably10% or higher, and particularly preferably 12% or higher. Meanwhile, inthe present specification, the term “(co)polymer” refers to homopolymerand/or copolymer.

In accordance with another aspect of the present invention, there isprovided a molding material for laser welding, comprising athermoplastic resin (A) which comprises:

a rubber-reinforced resin (A1) obtained by polymerizing a vinyl monomerin a presence of a rubber-like polymer (a),

-   -   or a composition (A2) comprising said rubber-reinforced resin        (A1) and a (co)polymer (b) of a vinyl monomer,    -   wherein said rubber-like polymer (a) dispersed in said        thermoplastic resin has a weight average particle size of 50 to        220 nm. Preferably, the rubber-like polymer (a) contained in the        molding material comprises particles of 300 nm or larger in        diameter in an amount of 0 to 20 wt % relative to 100 wt % of        the component (a).

In accordance with still another aspect of the present invention, thereis provided a molded article for laser welding, which is formed of theabove-described molding material for laser welding.

BEST MODE FOR CARRYING OUT THE INVENTION

The thermoplastic resin (A) for use in the present invention containseither a rubber-reinforced resin (A1) obtained by polymerizing a vinylmonomer in a presence of a rubber-like polymer (a), or a composition(A2) comprising the rubber-reinforced resin (A1) and a (co)polymer (b)of a vinyl monomer.

The component (A1) for use in the present invention is preferably arubber-reinforced vinyl resin obtained by polymerizing 95 to 30 wt % ofa vinyl monomer in a presence of 5 to 70 wt % of a rubber-like polymer(a). (In this case, the total of the rubber-like polymer (a) and thevinyl monomer is 100 wt %.)

Examples of the rubber-like polymer (a) include diene (co)polymers suchas polybutadiene, butadiene-styrene copolymer, butadiene-acrylonitrilecopolymer, butadiene-acryl copolymer, styrene-butadiene-styrene blockcopolymer, styrene-isoprene-styrene block copolymer, andisobutylene-isoprene copolymer, hydrogenated products of these diene(co)polymers, ethylene-α-olefin or ethylene-α-olefin-non-conjugateddiene copolymers (for example, ethylene-propylene-copolymer,ethylene-propylene-non-conjugated diene copolymer, ethylene-butene-1copolymer, ethylene-butene-1-non-conjugated diene copolymer),polyurethane rubbers, acryl rubbers, and silicone rubbers. These may beused singly or in combination of two or more. Of these rubber-likepolymers, preferred are diene (co)polymers, hydrogenated products ofdiene (co)polymers, ethylene-α-olefin orethylene-α-olefin-non-conjugated diene copolymers, acryl rubbers andsilicone rubbers, and diene (co)polymers are particularly preferred.

The rubber-like polymer (a) is present in the rubber-reinforced resin(A1) of the present invention in an amount of 5 to 70 wt %, preferablyin an amount of 5 to 65 wt %. If the amount of the rubber-like polymer(a) is less than 5 wt %, then impact resistance is decreased. If it isgreater than 70 wt %, appearance of molded articles is deteriorated.

The rubber-like polymer (a) dispersed in the rubber-reinforced resin(A1) of the present invention has a weight average particle sizetypically in the range of 50 to 220 nm, preferably 80 to 210 nm, morepreferably 100 to 200 nm, and particularly preferably 150 to 190 nm. Ifthe weight average particle size is larger than 220 nm, laser lighttransmittance of the molding material is lowered. As a result, itbecomes difficult for the molding material to transmit laser light forlaser welding. If the weight average particle size is less than 50 nm,impact resistance is degraded. To ensure uniform transmittance of laserlight, it is preferred that the rubber-like polymer (a) comprisesparticles of 300 nm or larger in diameter in an amount of 0 to 20 wt %relative to 100 wt % of the component (a).

The rubber-like polymer (a) for use in the present invention ispreferably one obtained by emulsion polymerization. The molding materialthat satisfies the above-described particle size requirements can beproduced, for example, by suitably setting conditions of thepolymerization so that the latex produced during the emulsionpolymerization of the rubber-like polymer (a) satisfies theabove-described particle size requirements. Alternatively, therubber-like polymer that satisfies the above particle size requirementscan be obtained by properly mixing a rubber-like polymer consisting oflatex having a small weight average particle size with a rubber-likepolymer consisting of latex having a large weight average particle size.

The vinyl monomer used in the component (A1) of the present inventionpreferably comprises at least one monomer selected from the groupconsisting of aromatic vinyl compounds, vinyl cyanide compounds, andother vinyl compounds that are copolymerizable with these compounds.

Examples of the aromatic vinyl compound include styrene,α-methylstyrene, o-methylstyrene, p-methylstyrene, vinyltoluene,methyl-α-methylstyrene, styrene bromide, and hydroxystyrene. Of these,styrene and α-methylstyrene are preferred.

Examples of the vinyl cyanide compound include acrylonitrile andmethacrylonitrile. Of these, acrylonitrile is preferred.

Examples of other vinyl monomers that are copolymerizable with aromaticvinyl compounds or vinyl cyanide compounds include, for example,(meth)acrylates and maleimide compounds, as well as unsaturatedcompounds containing various functional groups such as acid anhydridegroup-containing unsaturated compounds, hydroxyl group-containingunsaturated compounds, carboxyl group-containing unsaturated compounds,epoxy group-containing unsaturated compounds, and oxazolinegroup-containing unsaturated compounds. The term “(meth)acrylic acid” asused herein refers to acrylic acid and/or methacrylic acid.

Examples of the (meth)acrylate include methyl acrylate, ethyl acrylate,butyl acrylate, methyl methacrylate, ethyl methacrylate, and butylmethacrylate.

Examples of the maleimide compounds include maleimide,N-methylmaleimide, N-butylmaleimide, N-phenylmaleimide,N-(4-hydroxyphenyl)maleimide, and N-cyclohexylmaleimide. These maleimidecompounds may be introduced by a method in which maleic anhydride iscopolymerized, and then followed by imidation.

Examples of the acid anhydride group-containing unsaturated compoundinclude maleic anhydride, itaconic anhydride, and citraconic anhydride.

Examples of the hydroxyl group-containing unsaturated compound include3-hydroxy-1-propene, 4-hydroxy-1-butene, cis-4-hydroxy-2-butene,trans-4-hydroxy-2-butene, 3-hydroxy-2-methyl-1-propene,2-hydroxyethylacrylate, 2-hydroxyethylmethacrylate, hydroxystyrene, andN-(4-hydroxyphenyl)maleimide.

Examples of the carboxyl group-containing unsaturated compound includeacrylic acids and methacrylic acids.

Examples of the epoxy group-containing unsaturated compound includeglycidyl acrylates, glycidyl methacrylates, and allyl glycidyl ethers.

Examples of the oxazoline group-containing unsaturated compound includevinyloxazolines.

The above-described vinyl monomers can be used singly or in combinationof two or more.

Preferred vinyl monomers are those containing an aromatic vinyl compoundas an essential component. Examples include styrene, a combination ofstyrene and acrylonitrile, a combination of α-methylstyrene,acrylonitrile and methylmethacrylate, and a combination of styrene andmethylmethacrylate. Particularly preferred are combinations of aromaticvinyl compounds and vinyl cyanide compounds, in particular, acombination of styrene and acrylonitrile.

Blending proportion of the aromatic vinyl compound to the vinyl cyanidecompound is preferably 100-50/0-50 wt % as aromatic vinyl compound/vinylcyanide compound, more preferably 95-50/5-50 wt %, and particularlypreferably 75-65/25-35 wt %. Blending proportion of the othercopolymerizable monomers is 0 to 50 wt %, preferably 0 to 40 wt %relative to the component (A1).

The amount of the vinyl monomer relative to the component (A1) of thepresent invention is 30 to 95 wt %, preferably 35 to 95 wt %. If theamount is greater than 95 wt %, then impact resistance is decreased. Ifit is less than 30 wt %, appearance of molded articles is degraded.

The component (A1) of the present invention can be polymerized by use ofknown polymerization processes such as emulsion polymerization, bulkpolymerization, solution polymerization, suspension polymerization, andcombinations thereof. One obtained by emulsion polymerization isparticularly preferred in order to achieve the object of the presentinvention.

Upon production by the emulsion polymerization, a polymerizationinitiator, a chain transfer agent, an emulsifier, and water are used.These may be any of known ones. Polymerization of the vinyl monomer inthe presence of the rubber-like polymer (a) may be effected by addingthe vinyl monomer as a whole, discontinuously or continuously to theentire amount of the rubber-like polymer (a), or these additiontechniques may be combined. Alternatively, all or part of therubber-like polymer (a) may be added and polymerized during thepolymerization process.

Examples of the polymerization initiator include, for example, cumenehydroperoxide, diisopropylbenzene hydroperoxide, potassium persulfate,azobisisobutylonitrile, benzoyl peroxide, lauroyl peroxide,t-butylperoxy laurate, and t-butylperoxy monocarbonate.

Examples of the chain transfer agent include, for example, octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan, n-hexylmercaptan,tetraethylthiuram sulfide, acrolein, methacrolein, allyl alcohol, and2-ethylhexylthioglycol.

Examples of the emulsifier used in the emulsion polymerization processinclude, for example, sulfuric acid esters of higher alcohols,alkylbenzenesulfonic acid salts such as sodium dodecylbenzenesulfonate,aliphatic sulfonic acid salts such as sodium lauryl sulfate, anionicsurfactants such as salts of higher aliphatic carboxylic acids, salts ofrosin acids and salts of phosphoric acids, and known nonionicsurfactants.

In the emulsion polymerization process, a coagulating agent is generallyused to obtain powder which is then washed with water and dried to givepowdery rubber-reinforced resins. The coagulating agent used for thispurpose may be an inorganic salt such as calcium chloride, magnesiumsulfate, and magnesium chloride, or an acid such as sulfuric acid,hydrochloric acid, and acetic acid.

In the bulk polymerization, solution polymerization and suspensionpolymerization processes, various solvents, suspending agents,polymerization initiators, chain transfer agents, and other agents areused. These agents may be any of known agents.

When the component (A1) of the present invention is obtained by emulsionpolymerization, the rubber-like polymer is, in most cases, one obtainedby emulsion polymerization. In such cases, the gel content of therubber-like polymer is typically 98 wt % or less, preferably 40 to 98 wt%, more preferably 50 to 95 wt %, and particularly preferably 60 to 90wt %. When the gel content is 40 to 98 wt %, thermoplastic resincompositions which provide molded articles particularly excellent inimpact resistance and surface appearance can be obtained.

In determining the above-described gel content, 1 gram of therubber-like polymer is added to 100 ml of toluene. The mixture isallowed to stand for 48 hours at room temperature and is then filteredthrough a 100 mesh screen (weight=W₁). The insoluble matter in tolueneand the screen are dried under vacuum at 80° C. for 6 hours and areweighed (weight=W₂). The gel content can then be determined by thefollowing equation:Gel content (%)=[{W ₂(g)−W ₁(g)}/1(g)]×100.The gel content can be adjusted by properly setting type and amount ofthe molecular weight-adjusting agent, time and temperature forpolymerization, and polymerization conversion rate, when the rubber-likepolymer is produced.

Graft ratio of the component (A1) of the present invention is preferably20 to 200 wt %, more preferably 30 to 150 wt %, and particularlypreferably 40 to 120 wt %. The graft ratio (%) can be obtained by thefollowing equation:Graft ratio (%)={(T−S)/S}×100In the above equation, T is determined as follows: 1 gram of thecomponent (A1) is added to 20 ml of acetone. The mixture is shaken by ashaker for 2 hours and is then centrifuged for 60 min (23,000 rpm) toseparate soluble and insoluble matters. T is then given as the weight(g) of the insoluble matter. S is the weight (g) of the rubber-likepolymer present in 1 gram of the component (A1).

Limiting viscosity [η] of the acetone-soluble matter of the component(A1) (determined at 30° C. using methyl ethyl ketone as solvent) ispreferably 0.2 to 1.2 dl/g, more preferably 0.2 to 1 dl/g, andparticularly preferably 0.3 to 0.8 dl/g.

The component (A2) of the present invention is a composition obtained byblending the above-described rubber-reinforced resin (A1) with a(co)polymer (b) of a vinyl monomer.

The vinyl monomer used in the component (b) of the present inventionpreferably comprises at least one monomer selected from the groupconsisting of aromatic vinyl compounds, vinyl cyanide compounds, andother vinyl compounds that are copolymerizable with these compounds.

The aromatic compound and the vinyl cyanide compound may be any of thosedescribed with respect to the component (A1).

The other vinyl compounds that are copolymerizable with the aromaticcompound or the vinyl cyanide compound may be any of those describedwith respect to the component (A1).

These vinyl monomers may be used singly or in combination or two ormore.

Preferred (co)polymers (b) for use in the component (A2) of the presentinvention are those containing an aromatic vinyl compound as anessential component. Examples of the preferred (co)polymers include, forexample, homopolymers of aromatic vinyl compounds and copolymers ofaromatic vinyl compounds and at least one vinyl monomer selected fromvinyl cyanide compounds, (meth)acrylates, maleimide compounds and acidanhydride group-containing unsaturated compounds. Of these, particularlypreferred are copolymers composed of monomers containing an aromaticvinyl compound and a vinyl cyanide compound as essential components, inparticular, styrene-acrylonitrile copolymer,styrene-acrylonitrile-methyl methacrylate copolymer, andstyrene-acrylonitrile-maleimide compound copolymer.

Blending proportion of the aromatic vinyl compound to the vinyl cyanidecompound used in the component (b) is preferably 95-50/5-50 wt % asaromatic vinyl compound/vinyl cyanide compound, and more preferably75-65/25-35 wt %, from the viewpoint of balance between properties andprocessability.

In the present invention, the vinyl (co)polymer (b) is added to thecomponent (A2) in a predetermined amount so that the content of therubber-like polymer (a) originating from the component (A1) ispreferably 5 to 40 wt %, more preferably 5 to 35 wt %, and particularlypreferably 7 to 30 wt % relative to 100 wt % of the component (A2). Ifthe content of the rubber-like polymer (a) is smaller than theabove-specified range, then the impact resistance is deteriorated. Ifthe content is larger than the above-specified range, then appearance ofthe surface of molded articles is deteriorated.

The component (b) of the present invention can be produced by use ofknown polymerization processes such as emulsion polymerization, bulkpolymerization, solution polymerization, suspension polymerization, andcombinations thereof.

When the component (b) is produced by emulsion polymerization, theprocess described with respect to the component (A1) can be used.

The solvent used in solution polymerization may be an inactivepolymerization solvent used in common radical polymerization. Examplesinclude aromatic hydrocarbons such as ethylbenzene and toluene, ketonessuch as methyl ethyl ketone and acetone, halogenated hydrocarbons suchas dichloromethylene and carbon tetrachloride, acetonitrile,dimethylformamide, and N-methylpyrrolidone. Polymerization temperatureis preferably 80 to 140° C., more preferably 85 to 130° C., andparticularly preferably 90 to 120° C.

The polymerization may be carried out by thermal polymerizationtechnique without use of a polymerization initiator, or may be carriedout by use of a polymerization initiator. As the polymerizationinitiator, organic peroxides such as ketone peroxides, dialkylperoxides, diacyl peroxides, peroxy esters and hydroperoxides arepreferably used. Examples of the chain transfer agent includemercaptanes and α-methylstyrene dimer.

In bulk polymerization, all the polymerization initiators and the chaintransfer agents described with respect to the solution polymerizationcan be used.

The limiting viscosity [η] of the component (b) (determined at 30° C.using methyl ethyl ketone as solvent) is preferably 0.2 to 1.2 dl/g,more preferably 0.2 to 1 dl/g, and particularly preferably 0.3 to 0.8dl/g.

The component (A2) of the present invention can be produced by properlymixing the component (b) with the component (A1).

The amount of the monomer that ultimately remains in the component (A1)and the component (A2) is preferably 10,000 ppm or less, and morepreferably 5,000 ppm or less.

In the present invention, content of the rubber-like polymer (a) in thecomponent (A) is preferably 5 to 40 wt %, more preferably 5 to 35 wt %,and particularly preferably 7 to 30 wt % relative to 100 wt % of thecomponent (A). If the content is smaller than the above-specified range,then impact resistance is decreased. If the content is larger than theabove-specified range, then shapability and appearance of the surface ofmolded articles are degraded.

To the thermoplastic resin (A) of the present invention, may further beadded additives such as inorganic fillers, metal powders, reinforcingagents, plasticizers, compatibilizers, heat stabilizers, lightstabilizers, antioxidants, UV absorbers, dyes, pigments, antistats,lubricants, and flame retardants, depending on intended purpose andapplication, as long as light transmittance is not affected.

To the thermoplastic resin (A) of the present invention, may further beadded other polymers (B) which include, for example, polycarbonateresins, polyester resins, polyamide resins, polyamide elastomers,polyester elastomers, polyethylene, polypropylene, polyphenylene ethers,polyarylene sulfides, POMs (polyacetals), phenol resins, epoxy resinsand LCPs (liquid crystal polymers), without departing from the purposesof the present invention.

The molding material of the present invention can be produced by meltingand kneading together the respective components by various extruders,Henschel mixer, Banbury mixer, kneader, roll, feeder ruder or the like.Production processes using an extruder, Henschel mixer, or Banbury mixerare preferable.

Further, when the respective components are kneaded, all the componentsmay be kneaded at once, or the components may be gradually fed andkneaded in multiple steps using an extruder, Henschel mixer, or Banburymixer.

The products kneaded in Henschel mixer, Banbury mixer, kneader or thelike may be further made into pellets in an extruder.

The molding material of the present invention can be molded into moldedarticles by any of known molding techniques, including injectionmolding, press molding, sheet extrusion molding, vacuum molding, contourextrusion molding, and expansion molding.

The molded article of the present invention can be laser-welded withanother resinous molded article by laying the present molded article ona laser-absorbing resinous molded article and irradiating the presentmolded article with laser light. The laser light which can be usedincludes laser light of glass:neodymium3+ laser, YAG:neodymium3+ laser,ruby laser, helium-neon laser, krypton laser, argon laser, H2 laser, N2laser and semiconductor laser. Of these, semiconductor laser ispreferred. The wavelength of the laser light is preferably 1060 nm orshorter although it may vary depending upon resinous molded articles. Ifthe wavelength of laser light is longer than 1060 nm, it becomesdifficult to melt the surfaces to be welded. Power of laser light ispreferably 5 to 100 W. The power of the laser light lower than 5 W istoo low to melt the surfaces to be welded of the resinous moldedarticles. The power higher than 100 W is excessive and may evaporate ordegenerate the molding material.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram showing the method for evaluation ofweldability.

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to examples. It should be construed that the present are notlimited to the following examples.

In the following examples, parts and percentages are on weight basisunless otherwise specified. In the examples, evaluations were made inthe following manner.

(1) Evaluation Method

(1-1) Measurement of Light Transmittance

Pellets that had been produced were pressed at 240° C. for 5 min to forma 4 mm thick, 10 mm wide sample piece. Using a spectrophotometer(MPS-2000, Shimadzu Corporation), the sample piece was measured fortransmittance of light at a wavelength of 808 nm.

(1-2) Weight Average Particle Size and Proportion of Particles Sized 300nm or Larger of Rubber-Like Polymer

Particle size of the rubber-like polymer was obtained by measuringparticle size of produced latex in a state of emulsion, using a particlesize analyzer UPA 150 (trade name) manufactured by Nikkiso Co., Ltd. Ithad previously been confirmed by electron microscopy that the measuredparticle size corresponds to the particle size of particles dispersed inthe resin. Proportion of particles sized 300 nm or larger of therubber-like polymer was determined relative to 100% of the wholerubber-like polymer.

(1-3) Graft Ratio of the Component (A) (Rubber-Reinforced Resin)

This was determined in the manner described above.

(1-4) Evaluation of Weldability

As shown in FIG. 1, a sample piece 2 fabricated in the same manner as in(1-1) was laid on a piece 1 to be welded. The piece 1 had the samedimension as the piece 2. Using a laser welder NOVOLAS-C manufactured byLeister, laser light was irradiated onto the sample piece 2 under thefollowing conditions to weld the sample piece 2 to the piece 1.

<Conditions for Laser Welding>

Laser power=16 A

Speed=30 mm/sec

Weld width=2 mm

Weld length=10 mm

Pressure=7 kg/cm²

With a tensile tester, one of the welded piece 1 and the sample piece 2was pulled in the direction indicated by an arrow in FIG. 1 at a speedof 2 mm/min while the other piece was fixed. State of destruction of theweld area 3 was observed and evaluated on weldability according to thefollowing criteria:

◯: Weld strength was high enough to break the piece body;

Δ: Peeling occurred at the interface of the pieces, and the piece bodywas also broken;

X: Peeling occurred at the interface of the pieces.

(2) Components of Thermoplastic Resin Composition Production Example a-1Production of Rubber-like Polymer 1

A 5-liter stainless steel autoclave equipped with a reflux condenser, astirrer, an additive feeder, a thermometer and the like was provided.150 parts of deionized water, 4.0 parts of higher fatty acid soap(sodium salt of fatty acids composed mainly of a fatty acid with 18carbon atoms), and 0.075 part of sodium hydroxide were placed in theautoclave. The atmosphere inside the autoclave was replaced withnitrogen and the mixture was heated to 68° C. while being stirred.Subsequently, 20% of a monomer mixture composed of 100 parts of1,3-butadiene (BD) and 0.3 parts of t-dodecylmercaptan (TDM) was added,followed by addition of 0.135 part of potassium persulfate. The mixturegenerated heat after a few minutes to indicate initiation ofpolymerization. One hour after the addition of potassium persulfate,continuous addition of the remaining 80% of the monomer mixture wasstarted. The monomer mixture was added over 6 hours. Following thecontinuous addition of the monomer mixture, the internal temperature wasraised to 80° C. and the reaction was allowed to proceed at thistemperature for 1 hour, and then the polymerization reaction wasterminated. The resulting rubber-like polymer latex had a weight averageparticle size of 180 nm. 2.0% of the particles were sized 300 nm ormore.

Production Example a-2 Production of Rubber-Like Polymer 2

Polymerization reaction was carried out in the same manner as inProduction Example a-1, except that 0.5 part of sodium carbonate wasadded at the beginning of the reaction. The resulting rubber-likepolymer latex had a weight average particle size of 500 nm. 80% of theparticles were sized 300 nm or more.

Production Examples A-1 through A-4 Production of Rubber-ReinforcedResins

Emulsion polymerization was carried out using the rubber-like polymers,styrene monomer, and acrylonitrile monomer in accordance with theproportions shown in Table 1. Subsequently, magnesium sulfate was addedto coagulate the reaction mixture, and the solid product was washed anddried to give a rubber-reinforced resin (Designated as ABS 1-4 inTables). The graft ratio of each rubber-reinforced resin was shown inTable 1.

Production Example A-5 Production of Styrene-Acrylonitrile Copolymers

Solution polymerization was carried out using styrene monomer andacrylonitrile monomer in accordance with the proportions shown in Table1, to give a styrene-acrylonitrile copolymer (Designated as AS1 in Table1).

TABLE 1 ABS1 ABS2 ABS3 ABS4 AS1 AS2 (Part by (Part by (Part by (Part by(Part by (Part by weight) weight) weight) weight) weight) weight)Rubber-like polymer 1*¹ 40 38 36 24 — — Rubber-like polymer 2*² — 2 4 16— — Styrene monomer 42 42 42 42 70 43 Acrylonitrile monomer 18 18 18 1830 — N-phenylmaleimide — — — — — 55 Maleic anhydride monomer — — — — — 2Weight average particle size (nm) of rubber-like polymer 180 196 212 308— — Proportion (%) of particles sized 300 nm or larger in the 2.0 5.99.8 33.2 — — particles of rubber-like polymer Graft ratio (%) 90 80 7060 — — *¹Weight average particle size = 180 nm *²Weight average particlesize = 500 nm

Examples 1-3, and Comparative Example 1

The respective components were loaded in a Henschel mixer in accordancewith the proportions shown in Table 2, along with 0.2 part of alubricant and 0.3 part of an antioxidant. After mixing, the mixture wasmelted and kneaded by a twin screw extruder (TEM50A, Toshiba MachineCo., Ltd.) at 220 to 250° C. to obtain a resin composition as pellets.The resin composition was then subjected to the measurement fortransmittance and the evaluation on weldability in the manners describedabove. Upon evaluation of weldability, a piece to be welded was preparedas follows: A molded article (light transmittance=lower than 1%) wasobtained by preparing a resin composition in the same manner asdescribed above except that 100 parts of a commercially available ABSresin (trade name: Techno ABS130) was used together with 0.2 part of thelubricant and 0.3 part of the antioxidant, and then molding theresultant resin composition in the same manner as in (1-1) above. Theresults are shown in Table 2.

Example 4

A resin composition was obtained in the same manner as in Example 1,except that a styrene-N-phenylmaleimide-maleic anhydride copolymer(Malecca MS-N (trade name), Denki Kagaku Kogyo K. K., designated as AS2in Tables) was used instead of the styrene-acrylonitrile copolymer. Thisresin composition was subjected to the measurement for transmittance andthe evaluation on weldability in the same manner as in Example 1. Theresults are shown in Table 2 below.

TABLE 2 Example Example Example Example Comparative 1 2 3 4 Example 1ABS1 (Part by weight) 50 — — 50 — ABS2 (Part by weight) — 50 — — — ABS3(Part by weight) — — 50 — — ABS4 (Part by weight) — — — — 50 AS1 (Partby weight) 50 50 50 — 50 AS2 (Part by weight) — — — 50 — Lighttransmittance (%) 32 17 10 29 3 Weldability evaluation ∘ ∘ Δ ∘ x

The resin compositions of Examples 1 through 4, each showing a lighttransmittance of 5% or higher, were all good in weldability. Incontrast, the resin composition of Comparative Example 1 having a lighttransmittance of lower than 5% did not transmit enough laser light toachieve laser welding. A comparison of weldability between Example 2 andExample 3 revealed that when the light transparency is 10% or higher,excellent laser weldability is achieved.

INDUSTRIAL APPLICABILITY

The rubber-reinforced resin with high transmittance of laser lightaccording to the present invention permits laser-welding of a moldedarticle molded from the rubber-reinforced resin to a molded articlemolded from a laser-absorbing resin.

1. A molding material for laser welding consisting essentially of: athermoplastic resin (A) consisting essentially of: a rubber-reinforcedresin (A1) obtained by polymerizing styrene and acrylonitrile in thepresence of a rubbery polymer (a) consisting essentially ofpolybutadiene, or a composition (A2) consisting essentially of saidrubber-reinforced resin (A1) and a (co)polymer (b) of styrene andacrylonitrile, wherein said rubbery polymer (a) is dispersed in saidthermoplastic resin, has a weight average particle size of 150 to 200nm, and comprises particles of 300 nm or larger in diameter in an amountof 2 to 20 wt % relative to 100 wt % of said component (a), said moldingmaterial having a laser light transmittance at a wavelength of 808 nm ina range of 5% to 32% when the material is molded into a 4 mm thicksample, and the proportion of styrene to acrylonitrile in saidthermoplastic resin (A) is from about 75-65/25-35 wt %.
 2. The moldingmaterial for laser welding according to claim 1, wherein said rubberypolymer (a) dispersed in said thermoplastic resin has a weight averageparticle size of 150 to 190 nm.
 3. The molding material for laserwelding according to claim 1, wherein said rubbery polymer (a) dispersedin said thermoplastic resin comprises particles of 300 nm or larger indiameter in an amount of 2 to 5.9 wt % relative to 100 wt % of saidcomponent (a).
 4. The molding material for laser welding according toclaim 2, wherein said rubbery polymer (a) dispersed in saidthermoplastic resin comprises particles of 300 nm or larger in diameterin an amount of 2 to 5.9 wt % relative to 100 wt % of said component(a).
 5. The molding material for laser welding according to claim 3,wherein said rubbery polymer (a) is obtained by mixing a rubber-likepolymer consisting of latex having a small weight average particle sizewith a rubber-like polymer consisting of latex having a large weightaverage particle size.
 6. The molding material for laser weldingaccording to claim 4, wherein said rubbery polymer (a) is obtained bymixing a rubber-like polymer consisting of latex having a small weightaverage particle size with a rubber-like polymer consisting of latexhaving a large weight average particle size.
 7. The molding material forlaser welding according to any one of claims 1 and 2-6, wherein saidthermoplastic resin (A) consists essentially of said rubber-reinforcedresin (A1).
 8. The molding material for laser welding according to anyone of claims 1 and 2-6, wherein said thermoplastic resin (a) consistsessentially of said composition (A2).
 9. The molding material for laserwelding according to claim 7, wherein said rubber-reinforced resin (A1)has a graft ratio of 20 to 200 wt %.
 10. The molding materials for laserwelding according to claim 8, wherein said rubber-reinforced resin (A1)has a graft ratio of 20 to 200 wt %.